Nanoparticle fillers and methods of mixing into elastomers

ABSTRACT

A nanoparticle includes a copolymer comprising a vinyl-aromatic monomer and a heterocyclic monomer. The copolymer is crosslinked with a multifunctional crosslinking agent polymerizable through an addition reaction. A nanoparticle and elastomer composition is disclosed. Several methods of mixing heterocyclic and non-heterocyclic monomer nanoparticles into an elastomer are also disclosed. These methods include mixing in a multi-elements static mixer and an intermeshing mixer with venting, among others.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/250,025, filed on Aug. 29, 2016, which in turn is a divisional ofU.S. application Ser. No. 13/731,666, filed Dec. 31, 2012, issued asU.S. Pat. No. 9,428,604, on Aug. 30, 2016, which in turn claims thebenefit of priority to the U.S. provisional application having the Ser.No. 61/582,226, filed on Dec. 30, 2011. These prior applications areherein incorporated by reference for all purposes.

FIELD

This disclosure relates to nanoparticles and methods of blending theminto polymeric matrices.

BACKGROUND

Various types of small particulate additives have been used in polymercompositions. For example, core-shell particles for use in plasticcompositions as impact modifiers have been in use for many years. Rubbercompositions may also include core-shell particles, as taught, forexample, by U.S. Pat. No. 6,437,050. Living anionic polymerizationmethods are known for making core-shell nanoparticles. These may beformed by crosslinking polymer chains that are formed into a micelle.Furthermore, certain functionalized nanoparticles have also beensynthesized.

As with any polymer composition, determining what functional groups onan additive will be useful with a particular polymer matrix is achallenge. In addition to the general unpredictability of the art, aparticular challenge with functionalized polymeric nanoparticles is tomaintain the stability of the particle suspension during thepolymerization formation and to maintain while compounding with apolymer matrix. Furthermore, challenges are also present for efficientand thorough blending of the particles into a polymer system withuniform distribution.

Rubber polymeric matrices, in particular, may be advantageously modifiedby the addition of various nanoparticles. The physical properties ofrubber moldability and tenacity can be improved through such additions.However, the simple indiscriminate addition of nanoparticles to rubberis likely to be inhomogeneous and cause degradation of the matrixmaterial. Moreover, only the selection of nanoparticles having suitablesize, material composition, and surface chemistry, etc., will improvethe matrix characteristics. An efficient technique for blending thenanoparticles into the rubber to maximize uniform distribution is alsodesirable.

SUMMARY

In an embodiment a polymeric nanoparticle includes a copolymercomprising a vinyl-aromatic monomer and a heterocyclic monomer. Thecopolymer is crosslinked with a multifunctional crosslinking agent thatis polymerizable through an addition reaction.

In another embodiment, a composition includes an elastomer and polymericnanoparticles, wherein each polymeric nanoparticle comprises a copolymerincluding a vinyl-aromatic monomer and a heterocyclic monomer. Thecopolymer is crosslinked with a multifunctional crosslinking agent thatis polymerizable through an addition reaction.

In another embodiment a method for making a composition includes thesteps of: mixing, in the substantial absence of solvent, a dryelastomer; and adding to the dry elastomer and mixing, in aqueoussolution, a nanoparticle latex that comprises polymerized mono-vinylmonomer-contributed units crosslinked with a multifunctionalcrosslinking agent that is polymerizable through an addition reaction.Optionally, an additional unsaturated elastomer that may be the same ordifferent as the dry unsaturated elastomer is mixed in. Thenanoparticles are present in a volume fraction of the composition ofabout 0.02 to about 0.50.

In another embodiment, a method for making a composition includes:blending (a) a polymeric nanoparticle latex comprising polymerizedmono-vinyl monomer contributed units crosslinked with a multifunctionalcrosslinking agent that is polymerizable by means of an additionreaction into (b) an elastomer latex, thereby forming a pre-blendednanoparticle latex, and then mixing the pre-blended nanoparticleelastomer latex into a dry unsaturated elastomer.

In another embodiment, a polymeric nanoparticle composition includesnanoparticles having a polymeric core including vinyl-aromaticmono-vinyl monomer contributed units crosslinked with a multifunctionalcrosslinking agent polymerizable through an addition reaction. Thepolymeric core is essentially free of units of unsaturation and has aweight average particle diameter of about 10 to about 500 nanometers asdetermined by field flow fractionation on a sample swollen in THFsolvent.

In another embodiment a method for making a polymeric nanoparticlecomposition includes: dissolving an elastomer in a solvent or providingan elastomer dissolved in solvent; mixing the elastomer in solution withan aqueous nanoparticle latex in a multi-elements static mixer to forman elastomer and nanoparticle latex mixture; then flash drying theelastomer and nanoparticle latex mixture upon exiting the mixer.

In another embodiment a method for making an elastomeric nanoparticlecomposition includes: mixing an elastomer with an aqueous nanoparticlelatex in an intermeshing mixer; venting the intermeshing mixer to removewater; and recovering the elastomeric nanoparticle composition.

The terms “a,” “an,” and “the” are used to mean “one or more” unless thecontext clearly indicates to the contrary.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plot of G′ and tan delta versus strain % corresponding toExamples 14 and 17

FIG. 2 is a plot of tan delta versus temperature corresponding toExamples 20-23.

FIG. 3 is a plot of G′ versus strain % corresponding to Examples 20-23.

FIG. 4 is a plot of tan delta versus strain % corresponding to Examples20-23.

FIG. 5 is ¹³C NMR spectra of A) styrene, ethyl styrene, and DVB monomersin liquid state, B) sodium lauryl sulfate in solid state, C)nanoparticles as described herein in solid state and including thesodium lauryl sulfate, and D) a styrene-butadiene copolymer mixed withthe nanoparticles shown in C), in solid state.

FIG. 6 is a plot of strain sweep (SS) versus tan delta corresponding toExamples 31-37.

DETAILED DESCRIPTION

Disclosed herein are emulsion synthesized nanoparticles that may befunctionalized, elastomer compositions incorporating such nanoparticles,and several techniques for incorporating functionalized orun-functionalized nanoparticles into elastomeric compositions. Incertain embodiments disclosed herein, the nanoparticles function as atleast a partial replacement for reinforcing filler in the elastomericcomposition.

In an embodiment, the nanoparticles are formed through aqueousfree-radical emulsion polymerization of a vinyl-aromatic monomer andcrosslinked with a multifunctional crosslinking agent that ispolymerizable through an addition reaction. In an embodiment, thenanoparticles are functionalized with a group that will promote polymerinteraction, but that will limit agglomeration of the functional groupson the particles to themselves, similar to the Payne effect that is seenwith silica. In an embodiment, this type of particle is a moderatedensity polymeric composition that is much less dense than typicalreinforcing fillers, such as carbon black or silica. Without being boundby theory, embodiments of the nanoparticles disclosed herein arebelieved to be a capable substitute for all or part of the carbon-blackor silica reinforcement.

In an embodiment the nanoparticles are a copolymer of a vinyl-aromaticmonomer and heterocyclic monomer, such as an oxazoline monomer. Thecopolymer is crosslinked with a cross-linking agent that ismultifunctional and polymerizable through an addition reaction.

The vinyl-aromatic monomer may, for example, be a monomer represented bythe formula

R² is selected from hydrogen, or substituted or unsubstituted, straightor branched, cyclic or acyclic C₃-C₈ alkyl groups. R³ is an alkyl groupselected from phenyl, naphthyl, pyridyl, or R² substituted phenyl,naphthyl, or pyridyl.

Further specific examples include styrene, alpha-methylstyrene, 1-vinylnaphthalene, 2-vinyl naphthalene, 1-alpha-methyl vinyl naphthalene,2-alpha-methyl vinyl naphthalene, vinyl toluene, isomers of vinyltoluene, 2-, 3-, and 4-substituted vinyl toluene, and 2-, 3-, or 4-ethylstyrene (ES) e, methoxystyrene, t-butoxystyrene, as well as alkyl,cycloalkyl, aryl, alkaryl, and aralkyl substituted aromatic groups, inwhich the total number of carbon atoms in the combined hydrocarbon isnot greater than 18.

In an embodiment, vinyl-aromatic monomer contributed units compriseabout 30 to about 99 weight percent of the total weight of thenanoparticles such as about 50% to about 95%, or about 55% to about 75%.

The multifunctional crosslinking agent that is polymerizable through anaddition reaction includes monomers that are at least bifunctional,wherein the two functional groups are capable of reacting with thevinyl-aromatic monomer. Examples of suitable cross-linking agentsinclude multiple-vinyl-aromatic monomers in general. Specific examplesof cross-linking agents include di- or tri-vinyl-substituted aromatichydrocarbons, such as diisopropenylbenzene, triisopropenylbenzene,divinylbenzene (DVB), trivinylbenzene, N,N′-m-phenylenedimaleimide,N,N′-(4-methyl-m-phenylene)dimaleimide, acrylates and methacrylates ofpolyhydric C₂-C₁₀ alcohols, acrylates and methacrylates of polyethyleneglycol having from 2 to 20 oxyethylene units, polyesters composed ofaliphatic di- and/or polyols, with maleic acid, fumaric acid, anditaconic acid. Multiple-vinyl-aromatics, such as divinylbenzene, provideexcellent properties for some applications.

In an embodiment the multifunctional crosslinking agent is present in anamount of about 1% to about 30% of the total combined weight of thecrosslinking agent and mono-vinyl-aromatic monomer, such as about 5% toabout 25% or about 10% to about 20%, or in another embodiment, up to60%, such as about 4% to about 45%, or about 8% to about 35%.

In an embodiment the multifunctional crosslinking agent is included in aweight equal to about 0.1 to about 20 weight percent of the heterocyclicmonomer contributed unit, such as about 0.1 to about 15%, about 0.5 toabout 5%, about 10 to about 20%, or about 7 to about 15%.

The heterocyclic monomer, may, for example, comprise a 4 to 8 memberedhydrocarbon ring including one, two, three, or four heteroatoms. Thering structure may include one or more units of unsaturation. Theheteroatoms may be selected from one or more of nitrogen, oxygen, andsulfur. The cyclic structure may have constituent groups, including agroup with a polymerizable double bond.

In an embodiment, the heterocyclic monomer is according to formula (II):

wherein R₁-R₅ are independently selected from the group consisting ofhydrogen, a branched or linear C₁-C₂₀ alkyl group, a branched or linearC₃-C₂₀, cycloalkyl group, a branched or linear C₆-C₂₀ aryl group and abranched or linear C₇-C₂₀ alkylaryl group. In addition to therequirements above, R₁ contains at least a polymerizable double bond.For example, R₁ may be an unsaturated isopropenyl group, a vinyl group,or a phenyl group substituted with an unsaturated moiety. The oxazolinemay be one of the vinyl oxazoline compounds disclosed in U.S. Pat. Nos.6,596,798 and 7,186,845 incorporated herein by reference. In anembodiment, the oxazoline monomer is 2-isopropenyl-2-oxazoline (IPO).

Without being bound by theory, the oxazoline functionality is believedto provide interaction with a functionalized polymer while notcontributing to agglomeration of the nanoparticle filler.

In an embodiment the nanoparticles include about 0.1 to about 30 weightpercent of the heterocyclic monomer contributed unit, such as about 0.1%to about 15%, about 0.5% to about 5%, about 10% to about 20%, or about7% to about 15%.

In an embodiment, the nanoparticles are not functionalized orcopolymerized with functional group containing monomers. Suchnanoparticles include a core comprising vinyl-aromatic monomercontributed units that are crosslinked with a multifunctionalcrosslinking agent that is polymerizable through an addition reaction.The vinyl-aromatic monomer and crosslinking agent are as describedabove. The term “core” used herein is not meant to imply that a separateouter layer must also be present.

In an embodiment, the nanoparticles disclosed herein have a polymericcore that is essentially free of units of unsaturation. Essentially freeas used herein means other reactants are absent to the extent theymaterially affect the basic and novel properties of the composition.

In an embodiment, the nanoparticles disclosed herein have a weightaverage diameter of about 10 nm to about 500 nm as measured by fieldflow fractionation (FFF) with the nanoparticles swollen in THF solvent,such as, for example, about 15 to about 300 nm, about 15 to about 100nm, about 25 to about 200 nm, or about 50 to about 100 nm. FFF analysismay also be performed on an aqueous solution of the nanoparticles, andthis will give particle diameters of non-swollen nanoparticles. Thesemeasurements are approximately 60% the size of the nanoparticles thatare swollen in THF, but this will vary depending on the degree ofcrosslinking.

In an embodiment, the nanoparticles disclosed herein have a densityranging from about 0.8 to about 1.5 g/cc, such as about 0.9 to about 1.2g/cc. The nanoparticles may have a density that is about 60% of thedensity of carbon black (CB) or silica fillers (approximately 1.8 g/ccfor CB and approximately 2.0 g/cc for silica). In embodiments, thenanoparticles have a density of about 30% to 90%, or 50% to 70% ofcarbon black or silica. This feature allows for a much lower weightreinforcing material with the same volume fraction (v_(f)) of filler andprovides lower rolling resistance of a tire tread. The nanoparticledensity may be affected by a number of factors including the use oftermonomer functional groups or the degree of crosslinking.

In an embodiment, the nanoparticles disclosed have a relatively highglass transition temperature (T_(g)), such as about 40° C. to about 200°C., such as about 150° C. to about 195° C., or about 100° C. to about150° C. T_(g) may be affected by a number of factors including thenature of the monomer contributed units in the nanoparticle and thedegree of crosslinking. In an embodiment, the nanoparticle T_(g) shouldbe at least high enough to withstand temperatures required forvulcanization and use in a tire tread, or for example, about 60° C. andabove, or about 120° C. and above.

In an embodiment, the nanoparticles are incorporated into an elastomerhaving unsaturation to form a well-distributed elastomeric composition.

Theelastomer may be selected from the group consisting of: conjugateddiene polymers, copolymers or terpolymers of conjugated diene monomersand monovinyl-aromatic monomers, or more specifically,poly(styrene-butadiene), polybutadiene, natural rubber, polyisoprene,poly(isoprene-styrene), poly(isoprene-butadiene),poly(styrene-isoprene-butadiene), nitrile rubber, halobutyl rubber,butyl rubber, and combinations thereof.

In an embodiment the elastomer is functionalized with a carboxylfunctional group. Other functional groups may also be used, such ashydroxyl, vinyl, hydroxylaromatics, (such as phenolics). The functionalgroup may be incorporated into the elastomer by polymerizing functionalmonomers or through other known means such as post polymerizationfunctionalization, or by functional terminators or initiators. Forexample, the elastomer may be carboxylated poly(styrene-butadiene).

In an embodiment, the elastomer has a number average molecular weight ofabout 100 kg/mol and higher, such as about 150 kg/mol to about 700kg/mol, about 200 kg/mol to about 500 kg/mol, or about 250 kg/mol toabout 450 kg/mol.

In an embodiment, the nanoparticles are present in the elastomercomposition in a volume fraction (vf) of about 0.02 to about 0.5, suchas, for example, about 0.05 to about 0.4, about 0.16 to about 0.35, orabout 0.24 to about 0.3. Notably, the nanoparticles can be used involume amounts that exceed the volume amounts that typical carbon blackor silica fillers can be effectively used in rubber compositions, suchas, for example volume fractions of about 0.20 to about 0.28, or about0.22 to about 0.26. Embodiments of the methods and compositionsdisclosed herein allow for a higher volume fraction of filler than isconventional with other reinforcing fillers.

Determining volume fraction of nanoparticles in a like elastomericmatrix can be difficult (e.g. when both the nanoparticles and theelastomeric matrix include the same monomer-contributed units) withexisting NMR analysis techniques. As disclosed in the Examples section amethod of analysis with 13C MAS NMR was developed to determine thenanoparticle volume fraction in a like rubber matrix.

In an embodiment, the unsaturated elastomer of the composition issynthesized by emulsion polymerization and may be dry or in a latex. Inanother embodiment, the unsaturated elastomer is synthesized by solutionpolymerization.

Depending on the amount used and the character of the nanoparticles andthe unsaturated elastomer, when the nanoparticle-filled composition iscompared to an identical composition with the exception that thenanoparticles replace carbon black filler, the composition may havesignificant reductions (e.g. 5% and greater) in compound density,reduced abrasion resistance, and 60° C. tan S.

Although the nanoparticles disclosed herein are expected to providereinforcement akin to a conventional filler, they do not self-associateand cause an increase in the Payne effect. An embodiment of thecomposition containing the nanoparticles may also include a portion ofreinforcing filler, such as silica, carbon black, and/or other mineralfillers.

Examples of reinforcing silica fillers which can be used in thevulcanizable elastomeric compositions of the present disclosure includewet silica (hydrated silicic acid), dry silica (anhydrous silicic acid),and calcium silicate. Such reinforcing fillers are commerciallyavailable. Other suitable fillers include aluminum silicate, andmagnesium silicate. In one embodiment, precipitated amorphouswet-process, hydrated silicas can be employed. For example, silica canbe employed in an amount of about 1 to about 80 phr, in an amount ofabout 5 to about 60 phr, or in an amount of about 10 to about 40 phr.Examples of commercially available silica fillers which can be used inthe present disclosure include, but are not limited to, HI-SIL 190,HI-SIL 210, HI-SIL 215, HI-SIL 233, and HI-SIL 243, produced by PPGIndustries of Pittsburgh, Pa., U.S.A. A number of useful commercialgrades of different silicas are also available from EVONIK (e.g., VN2,VN3), RHODIA (e.g., ZEOSIL 1165 MPO), and J. M. HUBER.

In one embodiment, the rubber compositions of the present disclosure canbe compounded with any form of carbon black, with silica, as describedabove, or with both carbon black and silica. The carbon black can bepresent, for example, in an amount ranging from about 1 to about 80 phr,such as, for example, in an amount of about 5 to about 60 phr, or in anamount of about 10 to about 40 phr. The carbon black can include anycommonly available, commercially-produced carbon black. In oneembodiment, carbon blacks having a surface area of at least 10 m²/g,such as, in the range of from 35 m²/g to 200 m²/g, can be used in thepresent disclosure. Among useful carbon blacks are furnace blacks,channel blacks, thermal blacks, and lamp blacks. A mixture of two ormore of the above blacks can be used in preparing the carbon blackproducts of the present disclosure. Examples of suitable carbon blacksuseful in the present disclosure include, but are not limited to, N-110,N-220, N-339, N-330, N-352, N-550, N-660, as designated by ASTMD-1765-82a.

In some embodiments, certain additional fillers can also be utilized inthe vulcanizable elastomeric compositions of the present disclosure,including mineral fillers, such as clay, talc, aluminum hydrate,aluminum hydroxide and mica. The foregoing additional fillers may, forexample, be utilized in an amount in the range of from about 0.1 toabout 40 phr.

Numerous coupling agents and compatibilizing agents are known for use incombining silica and rubber, and can also be employed in the presentdisclosure. Silica-based coupling and compatibilizing agents suitablefor use in the present disclosure include, but are not limited to,silane coupling agents containing polysulfide components, or structuressuch as, for example, trialkoxyorganosilane polysulfides, containingfrom about 2 to about 8 sulfur atoms in a polysulfide bridge such as,for example, bis-(3-triethoxysilylpropyl) tetrasulfide (“Si-69”),bis-(3-triethoxysilylpropyl) disulfide (“Si-75”), and a NXT silane. Inan embodiment the composition is free of silane coupling agents.

It will be readily understood by those skilled in the art that therubber composition can be compounded by methods generally known in therubber compounding art, such as mixing the various vulcanizablepolymer(s) with various commonly used additive materials such as, forexample, curing agents, activators, retarders and accelerators,processing additives, such as oils, resins (including tackifyingresins), plasticizers, pigments, additional fillers, fatty acids, zincoxide, waxes, antioxidants, anti-ozonants, and peptizing agents. Asknown to those skilled in the art, depending on the intended use of thesulfur vulcanizable and sulfur vulcanized material (rubbers), theadditives mentioned above are selected and commonly used in conventionalamounts.

One application for nanoparticle-containing rubber compounds is in tirerubber formulations for tire components, such as, for example, tiretreads, tire sidewalls, inner liners, carcass plies, et al. Vulcanizableelastomeric compositions according to the present disclosure can beprepared by mixing a rubber and a nanoparticle composition either aloneor with reinforcing fillers comprising silica, a carbon black, or amixture of the two. A rubber and nanoparticle composition can also bemixed in a pre-blended composition with subsequent addition toadditional rubber components. The composition can also comprise aprocessing aid and/or a coupling agent, a curing agent, and/or aneffective amount of sulfur to achieve a satisfactory cure of thecomposition.

Rubbers suitable for use to make tire rubber formulations according tothe present disclosure include, for example, conjugated diene polymers,copolymers or terpolymers of conjugated diene monomers andmonovinyl-aromatic monomers, or more specifically,poly(styrene-butadiene), polybutadiene, natural rubber, polyisoprene,poly(isoprene-butadiene), poly(styrene-isoprene),poly(isoprene-isoprene-butadiene), nitrile rubber, halobutyl rubber,butyl rubber, and combinations thereof. Other rubbers may also beadditionally utilized in the composition, including neoprene, siliconerubber, the fluoroelastomers, ethylene acrylic rubber,ethylene-propylene rubber, ethylene-propylene terpolymer, ethylene vinylacetate copolymer, epichlorohydrin rubber, chlorinatedpolyethylene-propylene rubbers, chlorosulfonated polyethylene rubber,hydrogenated nitrile rubber, and tetrafluoroethylene-propylene rubber.

In an embodiment of a method for making the nanoparticles disclosedherein, the nanoparticles are synthesized by free radical aqueousemulsion polymerization. For example, the nanoparticles may besynthesized by mixing a vinyl-aromatic monomer, such as those discussedabove, with a multifunctional crosslinking agent that is polymerizablethrough an addition reaction, such as those discussed above.

For example, an aqueous solution including vinyl-aromatic monomers, suchas divinylbenzene, styrene, and ethyl styrene monomers may be prepared.Antioxidants used to stabilize the supplied materials may be extractedwith a base, such as sodium hydroxide. Washing with distilled water maybe performed until a substantially neutral pH is obtained, such as a pHof about 6.5 to about 8, less than 7 to about 7.3. Subsequent to thewashing step, drying over a drying agent, such as anhydrous sodiumsulfate may be performed.

In an embodiment, a non-functionalized nanoparticle is synthesized. Inthis embodiment, a vinyl-aromatic monomer blend, including thecrosslinking agent, such as a DVB/Styrene/Ethyl Styrene monomer blend isadded to oxygen-free water. A surfactant, such as sodium dodecyl sulfateor other common surfactants, is added. The mixture is then stirred whileheating. The pH of the mixture may be controlled by adding a base suchas sodium bicarbonate. In an embodiment, a radical generating initiator,such as potassium persulfate or other free radical initiator known tothose in the art, is then added to start the polymerization reaction.After polymerization occurs, the reaction is terminated by adding aquenching or terminating agent. For example, aqueous solutions of sodiumsalt diethyldithiocarbamic acid, dimethyldithiocarbamic acid, Na₂SO₃,1,4-hydroquinone, or other known quenching or terminating agents may beused.

In another embodiment, a functionalized nanoparticle is synthesized. Inthis embodiment, a vinyl-aromatic monomer blend, including thecrosslinking agent, such as a DVB/styrene/ethyl styrene monomer blend isadded to oxygen free water. A functional monomer, such as the oxazolinemonomer discussed above, is also added. A surfactant, such as sodiumdodecyl sulfate or other common surfactants, is added. The mixture isthen stirred while heating. The pH of the mixture may be controlled byadding a base such as sodium bicarbonate. A radical generatinginitiator, such as potassium persulfate or a free radical initiatorknown to those in the art, is then added to start the polymerizationreaction. After polymerization occurs, the reaction is terminated byadding a quenching or terminating agent. For example, aqueous solutionsof sodium salt diethyldithiocarbamic acid, dimethyldithiocarbamic acid,such as sodium hyposulfate, or other known quenching or terminatingagents may be used.

The functional monomer can be added at the same time as the monomer andthe crosslinking agent.

Four exemplary methods for making a composition including thenanoparticles and an unsaturated elastomer are provided herein. Thenanoparticles and elastomers blended by these methods, may, for example,be the nanoparticles and elastomers disclosed herein. Such as, forexample, the nanoparticles comprising polymerized mono-vinylaromaticmonomers crosslinked with a multifunctional crosslinking agentthat is polymerizable through an addition reaction.

In a first embodiment of the method, the unsaturated elastomer may bedissolved in a suitable solvent such as hexane, and then this solutionis mixed with the aqueous nanoparticle latex in a multi-elements staticmixer. The static mixer should have sufficient elements to produce anemulsion that may be flash dried directly upon exiting the mixer. Thenumber of elements necessary for producing such an emulsion may bereadily determined by those of skill in the art. Flash drying can beaccomplished by flash evaporation of the solvent at high temperatures,such as from about 100° to about 160° C.

This first embodiment corresponds to the following mixing method.Dissolving an unsaturated and uncured elastomer in a solvent. Then,mixing the elastomer in solution with an aqueous nanoparticle latex in amulti-elements static mixer to form an elastomer and nanoparticle latexmixture. Upon exiting the mixer the elastomer and nanoparticle latexmixture is flash dried.

A second embodiment includes adding a stable, aqueous latex of theunsaturated elastomer to a mildly-stirred, stable, aqueous nanoparticlelatex to give a homogenous blend of the two lattices. In an embodiment,this blend can then be desolventized by: (a) evaporation, (b)coagulation with salts or polar alcohols, or (c) flash evaporation fromabout 60° to about 160° C. This blend may be referred to as apre-blended nanoparticle elastomer latex, as in an embodiment it isadded to and subsequently blended with a dry elastomer.

This second embodiment corresponds to the following mixing method.Blending (a) a polymeric nanoparticle latex comprising polymerizedmono-vinyl monomers crosslinked with a multifunctional crosslinkingagent that is polymerizable through an addition reaction into (b) anunsaturated elastomer latex to thereby form a pre-blended nanoparticleelastomer latex; and then mixing the pre-blended nanoparticle elastomerlatex into a dry unsaturated elastomer. In an embodiment, prior toblending into the dry unsaturated elastomer, the pre-blendednanoparticle-elastomer latex is dried by known techniques to give anelastomeric nanoparticle blend, such as by coagulation or drum drying.

A third approach involves first introducing a dry, solid, solvent-free,unvulcanized, unsaturated elastomer to a heated mixer such as aBrabender forming a viscous mass of elastomer. Then adding an aqueousnanoparticle latex to the viscous mass of elastomer while maintainingmixing at a speed from 10 to 300 rpms and allowing the water in thenanoparticle latex to be vented off. The heating can vary from about100° to about 180° C. with the speed varying to prevent excess foamingof the mixture.

The third method described above corresponds to the following mixingmethod: blending, in the substantial absence of solvent, a dry, uncured,unsaturated elastomer. Then a nanoparticle latex (nanoparticles in anaqueous latex) is added and mixed into the composition. Thenanoparticles comprise polymerized mono-vinyl monomer contributed unitscrosslinked with a multifunctional crosslinking agent that ispolymerizable through an addition reaction

A fourth approach for mixing nanoparticles and elastomers comprisesadding a nanoparticle latex (nanoparticles in an aqueous latex) and anelastomer into a vented, intermeshing mixer. The elastomer may be dry,uncured, and unsaturated. However, in an embodiment, the elastomer isnot necessarily dry, and may be in an aqueous latex form also.

An intermeshing mixer imparts high shear forces through the design androtation of the rotors of the mixing apparatus. Example intermeshingmixers include twin-screw extruders or tandem mixers.

The intermeshing mixing imparts additional energy to the compositionbeing mixed. For example, this energy may be measured by the differencein the initial temperature and the drop or dump temperature of thecomposition undergoing mixing. In an embodiment, the temperaturedifference is about 5° C. to about 50° C., such as, for example, about10° C. to about 35° C., or about 15° C. to about 30° C.

While the following will be dependent on the mass of the composition andthe size of the mixer, inter alia, some example settings are provided.The intermeshing mixer may be set to various power levels such as about10 to about 100 rpm, about 15 to about 90 rpm, or about 20 to about 60rpm. The composition may be resident in the intermeshing mixer for atime of about 1 to about 5 minutes, such as, for example, about 2 toabout 4 minutes, or about 2.5 to about 3.5 minutes.

The intermeshing mixer is vented, so as to allow removal of the waterfrom the nanoparticle latex portion. To properly vent and remove thewater, the mixture should be heated to at least the boiling point ofwater. This is facilitated by a vented intermeshing mixer, which, unlikesome other conventional elastomer mixers has reduced foaming of latexmixtures when the temperature is raised above 100° C.

In an embodiment, the intermeshing mixer has several zones. A zone isprovided for feeding the mixing components, such as the elastomer andnanoparticle latex. In an embodiment, in the feeding zone, the elastomeris continuously mixing while the aqueous nanoparticle latex is added.Example temperatures for the feeding zone are ambient temperature toless than 100° C., such as about 25° C. to about 90° C. or about 40° C.to about 60° C.

In an embodiment, in subsequent zones, the temperature of the mixture inthe intermeshing mixer is held at or above 100° C. For example, in thesezones the temperature of the mixture may range from about 100° C. toabout 180° C., such as, for example, about 155° C. to about 175° C., orabout 115° C. to about 150° C.

In an embodiment, a second zone is closed while the compositionundergoes mixing. A third zone is open for venting. A fourth zone isclosed for additional mixing, and the mixture is extruded in a finalzone as a dry elastomer and nanoparticle mixture. If necessary to removelatent water or for other purposes, the extrudate may be re-cycledthrough the intermeshing mixer for several passes until the dryelastomer and nanoparticle mixture is substantially free of water, e.g.less than 5%, less than 3%, or less than 1% water. In an embodiment, thecomposition undergoes multiple passes through the extruder, such as, forexample, two, three, four, or five passes through the extruder.Additional passes through a vented extruder allow for a greater amountof water to be vented, thereby concentrating the nanoparticle fillervolume fraction in the elastomeric composition.

In an embodiment, prior to the intermeshing mixing step, thenanoparticle latex is concentrated by vacuum concentration to furtheraid in reducing the water content of the composition.

The vented intermeshing mixer method aids in handling of the components,provides good dispersion, and facilitates higher volume fractions ofnanoparticles, e.g. about 0.26 to about 0.35, or about 0.3 to about 0.5.

While intermeshing mixing is inherently difficult to accuratelycalculate a volume fraction of filler, with the ¹³C MAS NMR methoddisclosed below, the weight percent of the nanoparticles can determinedby solid state NMR such that the composition of the extrudate can beaccurately measured and adjusted to a desired of by normal rubber mixingtechniques. This allows the preparation of a master batch such that itcan be conveniently used for blending with other fillers or polymers toprovide improved properties. For example, ¹³C MAS NMR may be performedon a dry elastomer and nanoparticle composition and using this data thevolume fraction of nanoparticles in the dry elastomer and nanoparticlecomposition can be determined. With this knowledge, the v_(f) of thecomposition can be adjusted by conventional rubber mixing techniques toa desired level by mixing in additional elastomer.

In an embodiment, the above methods may further comprise adding anadditional unsaturated elastomer that may be the same or different asthe dry unsaturated elastomer. In an embodiment, the nanoparticles andrubber latex or the dry nanoparticles and elastomer mixture are added asa pre-blend to the additional unsaturated elastomer. Optionally,additional mixing steps may be performed at elevated temperatures toallow water to be removed while leaving a dry nanoparticle filledrubber. The subsequently mixed dry unsaturated elastomer may besynthesized by solution polymerization or emulsion polymerization,natural rubber, or polymers synthesized by other polymerizationprocesses. Thus, these methods of mixing are versatile in the types ofelastomers that can be used.

In an embodiment, the methods for making a nanoparticle-filledelastomeric composition further include, adding and mixing in to thecomposition, at a temperature of up to about 190° C., or up to about180° C., additional components for cured elastomer compositions, knownto those of skill in the art, including those discussed above, forexample, silica, carbon black, oil, resin, wax, coupling agents, andcombinations thereof.

A curing agent may be added at a temperature of up to about 50° C. toabout 110° C., and the composition may be cured at a temperature ofabout 140° C. to about 200° C.

The dry nanoparticle-elastomer composition may be compounded by methodsgenerally known in the rubber compounding art, such as mixing theunsaturated elastomer and the nanoparticles with conventional amounts ofvarious commonly used additive materials, using standard rubber mixingequipment and procedures.

A vulcanized rubber product may be produced by thermomechanically mixingthe rubbery matrix polymer containing nanoparticles, and variousingredients in a sequentially step-wise manner in a rubber mixer,followed by shaping and curing the composition. By thermomechanicalmixing, it is meant that various ingredients in the composition aremixed under high shear conditions where the composition autogenouslyheats up, with an accompanying temperature rise, as a result of themixing primarily due to shear and associated friction within thecomposition in the rubber mixer.

The composition of this invention can be used for various purposes andin various articles of manufacture, such as a tire component. Such tirecomponents can be built, shaped, molded and cured by various methodswhich are known and will be readily apparent to those having skill insuch art. In an embodiment, a molded unvulcanized tire component ischarged into a vulcanizing mold and then vulcanized to produce a tirecomponent, comprising the composition described above.

The following examples are included to provide additional guidance tothose skilled in the art in practicing the claimed invention. Theexamples provided are merely representative of the work that contributesto the teaching of the present application. Accordingly, these examplesare not intended to limit the invention, as defined in the appendedclaims, in any manner.

Examples 1-7

A 19% divinylbenzene (DVB) solution mixed with styrene (S) and ethylstyrene (ES) was prepared by mixing 55% DVB/ES with S. Antioxidants wereextracted with 10% aqueous sodium hydroxide. This was performed threetimes until no color appeared in the aqueous extract. Washing withdistilled water was then performed until a pH of about 7 was obtained.Drying over anhydrous sodium sulfate was performed before further use.The oxygen-free distilled water was prepared by boiling distilled waterwhile bubbling nitrogen gas through the liquid and then cooled whilecontinuing the nitrogen purge. Oxygen-free distilled water was used asthe reaction media and to prepare all reagents.

A Wyatt Technology instrument was used for the FFF analysis. The samplesfor FFF were prepared by dilution of the latex to approximatelyfive-tenths of a milligram of nanoparticles per 1 mL of water. Thesamples were then injected into the instrument thereby introducing about50 micrograms of nanoparticles into the sample chamber.

In each example, where applicable, pyrolysis GC-MS was used to identifythe DVB/S and IPO incorporation.

Pyrolysis GC-FID was used to confirm the particle composition in certainExamples. For the pyrolysis analysis, samples with known compositionswere used for the calibration of styrene, ethyl styrene anddivinylbenzene. The conditions used are shown below.

Pyrolysis unit: CDS 5250 Pyrolysis with the auto sampler

Gas chromatograph: Agilent 7890 GC system

Detector: Flame ionization detector (FlD)

Sample sizes use for the pyrolysis: about 1 mg

Pyrolyzer valve-oven temperature: 300° C.

Pyrolysis temperature: 700° C.

Pyrolysis time: 6 sec

Transfer line temperature: 300° C.

GC injection port temperature: 280° C.

GC split ratio: 1:50

GC column: HP-5MS (30 m×0.25 mm×0.5 11 μm film)

GC column flow rate: 2 mL/min

Air flow to the detector: 300 mL/min

H₂ flow to the detector: 30 mL/min

Make up N₂ gas to the detector: 30 mL/min

Table 1 below shows the temperature program of the GC column oven.

TABLE 1 Hold Total Temperature/° C. Rate ° C./min time/min time/minInitial 40 1 1 Final 260 15 10 25.7

All samples were run multiple times with blanks in between. U.S.provisional application 61/487,756 filed on May 19, 2011, filed asnon-provisional application U.S. Ser. No. 13/476,387, filed on May 21,2012, published as U.S. 2012/0296054, which provides a full discussionof the general pyrolysis method is herein incorporated by reference.

Example 1

To a 250 mL Erlenmeyer flask containing a 5 mm magnetic stir bar wasadded 68.02 grams of oxygen-free water. To this flask was then added22.61 grams of a 19.01% DVB/S mixture that contained 4.30 grams of DVB,14.79 grams of S and 3.52 grams of ES. This was followed by 0.19 g ofsodium bicarbonate and 3.20 g of sodium dodecyl sulfate. This mixturewas stirred slowly (about 120 rpm) with a magnetic stirrer while heatingin a water bath that was controlled at 60° C. At this time a whiteopaque mixture was obtained. Then 8.0 mL of a 0.037 M aqueous solution(from oxygen-free water) of potassium persulfate was added and thestirring speed was increased to 300 to 400 rpm. Within 30 minutes themixture went from a white opaque suspension to an almost translucentblue-white milky emulsion. The temperature of the water bath was held inthe 58° C. to 63° C. range for 7 hours before termination of thepolymerization with 0.6 mL of a 0.5 M aqueous solution of1,4-hydroquinone.

Upon cooling, no odor of DVB, S, or ES could be detected. The pHmeasured was about 7 by paper strip measurement. The calculated solidscontent of the latex was 24.923%. Field Flow Fractionation (FFF)measurement in THF as a solvent showed the following particle sizedistributions of d_(n)=21.4 nm, d_(w)=22.6 nm, and d_(z)=24.7 nm. Theparticles were swollen in the THF solvent. Further details are reportedin Table 2.

Example 2

Example 2 was prepared by the same method as Example 1, however, thecomponent amounts were varied and the potassium persulfate was added insolid form. The component details and particle measurements are reportedin Table 2.

Example 3

To a 2 L resin kettle containing an N₂ inlet tube and an electricstirrer with a paddle blade was added 542.40 grams of oxygen-freedistilled water. Then 1.53 grams of sodium bicarbonate and 25.77 gramsof sodium dodecyl sulfate were added while maintaining the nitrogenpurge, stirring at 150 rpm, and heating to 45° C. To this aqueoussolution was added 180.88 grams of 18.86% DVB/S mixture that had beenextracted free of antioxidant. Immediately after the monomers wereadded, 64 mL of a 0.037 M aqueous solution of potassium persulfate(prepared with oxygen free water) was added. A white emulsion wasinitially formed that became opaque within 30 minutes while furtherheating the emulsion to above 60° C. and stirring at about 400 rpm.After reacting for 4 hours the heating was stopped and 0.72 mL of a3.30M aqueous solution of 40% sodium salt of dimethyl dithiocarbamicacid was added.

Upon cooling, no odor of DVB, S or ES could be detected. The absence ofDVB, S, and ES was confirmed by GC analysis. The pH measured was about 7by a paper strip measurement.

The calculated polymeric solids were 22.19%. The maximum particle sizein the latex was determined by FFF measurement in THF as a solvent,which showed the following particle size distributions: d_(n)=20.8 nm,d_(w)=23.1 nm, and d_(z)=27.3 nm with a dispersion of 1.11. Furtherdetails are reported in Table 2.

Examples 4 and 5

Examples 4 and 5 were prepared by the same method as Example 1; however,the component amounts were varied. Further details are reported in Table2.

Example 6

To a 2 L resin kettle containing a N₂ inlet tube and an electric stirrerwith a paddle blade was added 541.70 grams of oxygen-free distilledwater. Then 2.88 grams of sodium bicarbonate and 27.65 grams of sodiumdodecyl sulfate were added while maintaining the nitrogen purge. Thecomponents were stirred at 150 rpm while heating to 45° C. To thisaqueous solution was added 160.0 grams of 18.92% DVB/S mixture that hadbeen extracted free of antioxidant and 29.5 grams of2-isopropenyl-2-oxazoline (IPO). Immediately after the monomers wereadded, 64 mL of a 0.037 M aqueous solution of potassium persulfate(prepared with oxygen free water) was added. A white emulsion wasinitially formed that became opaque within 10 minutes. The power wasinterrupted for 50 minutes at this point, just as the exothermicreaction began and the temperature reached 52° C. When the power wasrestored the stirring was continued at 670 rpm and the temperature wasincreased from 48 to 72° C. for the next hour before being reduced to450 rpm for 16 hours at the 72° C. After this time, heating was stoppedand 0.72 mL of a 3.30M aqueous solution of 40% sodium salt of dimethyldithiocarbamic acid was added.

Upon cooling, no odor of DVB, S, ES or IPO could be detected. Theabsence of DVB, S, ES, and IPO was confirmed by GC analysis. The pHmeasured was about 7 by a paper strip measurement. The particle size inthe latex was determined by FFF measurement in THF as a solvent andshowed the following distribution of THF swollen particle: d_(n)=76.6nm, d_(w)=161.7 nm and d_(z)=234.7 nm, with a dispersion of 2.11.Further details are reported in Table 2.

The calculated polymeric solids were 23.76%, which had a composition of14.86% IPO and 16.11% DVB. The incorporation of the IPO was confirmed bypyrolysis GC-FID.

Example 7

To a 250 mL Erlenmeyer flask containing a 5 cm magnetic stir bar wasadded 74.15 grams of oxygen free water, 22.61 grams of a 19.01% DVB/Smixture that contained 4.01 grams of DVB, 13.81 grams of S and 3.28grams of ES. This was followed by 0.26 g of sodium bicarbonate, 3.40 gof sodium dodecyl sulfate and 3.70 grams of 2-isopropenyl-2-oxazoline(IPO). This mixture was stirred slowly (about 120 rpm) with a magneticstirred while heating in a water bath that controlled at 60° C. At thistime a white opaque mixture was obtained. Then 8.0 mL of a 0.037 Maqueous solution (prepared from oxygen free water) of potassiumpersulfate was added and the stirring speed was increased to 300 to 400rpm. Within 30 minutes the mixture went from a white opaque suspensionto an almost translucent blue-white milky emulsion. The temperature ofthe water bath was held in the 58 to 63° C. range for 7 hours beforetermination the polymerization with 0.07 grams of the sodium saltdiethyl dithiocarbamic acid. Upon cooling no odor of DVB, S, ES or IPOcould be detected. The pH measured was ˜7 by paper strip measurement.The calculated functional crosslinked styrene content was 22.39% and thetotal solids of the latex was 25.94%, FFF (Field Flow Fraction)measurement in THF as the solvent showed the swollen particle sizedistributions of d_(n)=20.1 nm, d_(w)=23.2 nm and d_(z)=32.0 nm with adispersion of 1.15.

TABLE 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Water grams 68.0263.33 542.4 73.5 68.92 541.7 74.15 SLS grams 3.20 1.70 25.77 3.51 3.5027.65 3.40 NaHCO₃ grams 0.19 0.18 1.53 0.29 0.31 2.88 0.36 Extracted mixof Styrene (S) grams 65.45 27.34 132.00 132.20 132.10 132.20 65.45 55%DVB grams 34.58 4.68 68.88 69.34 69.36 69.34 34.58 % DVB in mix 19.018.04 18.86 18.92 18.94 18.92 19.01 S/DVB Mixture, grams 22.61 21.92180.88 24.6 25.17 169.4 21.11 DVB grams 4.30 1.76 34.11 4.66 4.77 31.984.01 Et Styrene (ES) grams 3.52 1.44 27.91 3.81 3.90 26.17 3.28 IPOgrams 0 0 0 2.14 2.86 29.50 3.70 DVB/hundred vinyl- 19.01 8.04 18.8617.41 17.00 16.11 16.18 aromatics, wt % IPO in particle, wt % 0 0 0 8.0010.20 14.86 14.91 K₂S₂O₈, grams 0.1 K₂S₂O₈, mL of 0.037M soln. 8.0 64.08.0 8.0 64.0 8.0 1,4-Hydroquinone, mL 0.5M 3 3 soln. Et₂NCS₂Na, grams0.07 Me₂NCS₂Na, mL of 3.30M 0.72 0.30 0.30 0.72 soln. Nanoparticles,g/100 mL 21.53 24.29 22.19 23.80 25.70 23.76 22.39 Total Weight, grams105.02 90.23 815.30 112.34 109.06 835.45 110.79 FFF particle size d_(n),ave nm 21.7 20.8 81.2 59.4 76.6 20.1 d_(w), ave nm 22.6 23.1 93.8 89.4161.7 23.2 d_(z), ave nm 24.7 27.3 113.8 220.1 234.7 32 Dispersion, w/n1.04 1.11 1.16 1.51 2.11 1.15

Examples 8-17

Latex samples of nanoparticles formed in Examples 3 and 6 were blendedwith emulsion-polymerized styrene-butadiene rubber (E-SBR) latexes andthen dried to form a polymer-filler composite with filler volumefraction of approximately 0.2 (100 phr of polymer and 30 phr ofnanoparticles). The E-SBR materials included non-functionalized E-SBRlatex, (ROVENE 4848 with rosin acid soap emulsifier (T_(g)=−38° C., 51%total solids, from Mallard Creek Polymers, Inc., Charlotte, N.C.) andcarboxylated E-SBR (ROVENE 5044 with anionic emulsifier (T_(g)=−35° C.;51% total solids; from Mallard Creek Polymers, Inc., Charlotte, N.C.).

The dried nanoparticle and polymer pre-blends were mixed in theformulation given below using a Brabender mixer having cam rotors thathave a 307 cm³ working volume. The nanoparticles were employed as theonly filler in the rubber and were also considered in combination withcarbon black (50/50 by volume). All of the final compounds were designedto have a filler volume fraction of approximately 0.2, which required alower phr amount of the nanoparticles than carbon black. This was due tothe lower density (approx. 1.1 g/cc) of the nanoparticles compared tocarbon black (approx. 1.8 g/cc). Test results are reported in Table 3and FIG. 1.

According to the disclosure herein, in certain embodiments, significantreductions (e.g. 5% and greater) in compound density, abrasion loss, and60° C. tan δ may be seen. Abrasion loss may be performed as disclosed inU.S. 2003/0127169, which is herein incorporated by reference.

The areas in the table marked N/A represent data which could not beacquired due to difficult de-molding of compounds sticking to the mixerand the mill. Testing denoted as SS was done in a strain sweep mode from0.25 to 14.75% E in 0.25% increments. TS was done by a temperature sweepfrom −80° C. to 100° C. in 5° C. increments.

TABLE 3 Example: 8 9 10 11 12 13 14 15 16 17 Carboxylated E-SBR (phr):100 100 100 100 100 E-SBR (phr): 100 100 100 100 100 Example 6nanoparticles 30 15 30 15 Example 3 nanoparticles 30 15 30 15 N339 CB(phr): 25 25 50 25 25 50 Stearic Acid (phr) 2 2 2 2 2 2 2 2 2 2 ZincOxide (phr) 2 2 2 2 2 2 2 2 2 2 Antioxidant (phr) 0.9 0.9 0.9 0.9 0.90.9 0.9 0.9 0.9 0.9 Sulfur (phr) 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2CBS Accelerator (phr) 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 t50% [171°C. Cure] (min): 11.5 9.5 7.1 5.8 5.1 8.3 5.4 4.9 4.2 2.5 ML1 + 4 @ 130°C.: 26.5 17.9 29.2 25.2 36.7 52.6 17.6 57.7 33.8 53.2 G′ [TS, 0° C., 10Hz, 2%] (MPa): 17.7 N/A 20.4 26.5 27.4 18.5 17.6 20.0 20.0 11.9 tanδ[TS, 0° C., 10 Hz, 2%]: 0.485 N/A 0.527 0.465 0.573 0.312 0.386 0.3980.475 0.572 G′ [TS, 60° C., 10 Hz, 2%] (MPa): 2.67 N/A 2.75 3.60 3.735.43 4.27 4.96 3.84 4.00 tanδ [TS, 60° C., 10 Hz, 2%]: 0.257 N/A 0.3000.315 0.347 0.175 0.224 0.223 0.287 0.334 Decrease in tanδ at 60° C.(%): 25.9 N/A 13.5 9.2 0.0 47.6 32.9 33.2 14.1 0.0 G′ [SS, 60° C., 10Hz, 5%] (MPa): 1.66 N/A 1.65 2.07 2.05 4.53 N/A 3.26 2.15 2.02 tanδ [SS,60° C., 10 Hz, 5%]: 0.315 N/A 0.362 0.375 0.376 0.234 N/A 0.293 0.3480.391 ΔG′ [SS, 60° C., 10 Hz, 0.03%-15%] (MPa): 0.72 N/A 1.23 2.67 2.334.83 N/A 4.36 3.14 3.62 50% Modulus@ 23° C.(MPa): 2.19 N/A 2.08 1.652.78 1.22 0.69 1.35 1.02 1.74 300% Modulus @ 23° C. (MPa): N/A N/A N/AN/A N/A 3.87 1.67 5.95 5.03 N/A Break Stress@ 23° C. (MPa); 6.4 N/A 6.06.1 7.1 5.3 4.8 6.3 6.1 7.8 Elongation at Break @ 23° C. (%): 197 N/A183 244 151 426 612 324 366 220 Wear Wt. Loss at 25% slip (g): 0.241 N/A0.281 0.241 0.280 0.089 0.061 0.128 0.126 0.173 Wear Resist. Improvementat 25% slip (%): 13.9 N/A −0.4 13.9 0.0 48.6 64.7 26.0 27.2 0.0 CuredCompound Density (g/cc): 1.009 N/A 1.085 1.088 1.162 1.007 1.004 1.0801.082 1.166 Decrease in Compound Density (%): 13.2 N/A 6.6 6.4 0.0 13.613.9 7.4 7.2 0.0

Example 18

To a 2 L resin kettle containing a N₂ inlet tube and an electric stirrerwith a paddle blade was added 566.19 grams of oxygen-free distilledwater. Then, 1.51 grams of sodium bicarbonate and 25.05 grams of sodiumdodecyl sulfate were added while maintaining the nitrogen purge,stirring at about 150 rpm, and heating to 48° C. To this aqueoussolution was added 195.51 grams of 18.98% DVB/S mixture that had beenextracted free of antioxidant and 28.12 grams of IPO. Immediately afterthe monomers were added, 32 mL of a 0.037 M aqueous solution ofpotassium persulfate (prepared with oxygen-free water) was added. Awhite emulsion was initially formed that became opaque within 10minutes. The stirring was continued at 380 rpm and the temperature wasincreased to 83° C. for the next hour. Then the heating was stopped and0.72 mL of a 3.30M aqueous solution of 40% sodium salt of dimethyldithiocarbamic acid was added.

Upon cooling, no odor of DVB, S, ES or IPO could be detected. Theabsence of DVB, S, ES and IPO was confirmed by GC analysis.

A total of 798.24 g of latex was obtained with a pH of about 7, asmeasured by a paper strip. The calculated polymeric solids were 23.34%,which had a composition of 9.90% IPO and 16.59% DVB. The incorporationof the IPO was confirmed by pyrolysis GC. The particle size in the latexwas determined by FFF measurement, as discussed above, in THF as asolvent and showed the following distribution of THF swollen particle:d_(n)=15.3 nm, d_(w)=17.2 nm and d_(z)=19.2 nm with a dispersion of1.12. Further details of the blend are presented in Table 4.

Example 19

To a 2 L resin kettle containing an N₂ inlet tube and an electricstirrer with a paddle blade was added 590.16 grams of oxygen-freedistilled water. Then 1.56 grams of sodium bicarbonate and 26.29 gramsof sodium dodecyl sulfate were added while maintaining the nitrogenpurge, stirring at 150 rpm, and heating to 45° C. To this aqueoussolution was added 196.98 grams of 18.81% DVB/S monomer mixture that hadbeen extracted free of antioxidant. Immediately after the monomers wereadded, 32 mL of a 0.037 M aqueous solution of potassium persulfate(prepared with oxygen free water) was added. A white emulsion wasinitially formed that became opaque within 30 minutes while furtherheating to 83° C. and stirring at about 360 rpm. After reacting for 4hours, the heating was stopped, and 0.72 mL of a 3.30M aqueous solutionof 40% sodium salt of dimethyl dithiocarbamic acid was added.

Upon cooling, no odor of DVB, S or ES could be detected. The absence ofDVB, S, and ES was confirmed by GC analysis.

The isolated weight of latex was 823.82 g and it had a pH of about 7 asmeasured by a paper strip. The calculated polymeric solids were 23.24%and 26.54% total solids. The particle size in the latex was determinedby FFF measurement, as discussed above, using THF as a solvent andshowed a distributions of d_(n)=18.7 nm, d_(w)=19.9 nm and d_(z)=21.0 nmwith a dispersion of 1.06. The FFF analysis was also performed on anaqueous solution of the nanoparticles that did not cause thenanoparticles to swell, and the measurements were approximately 60% thesize of the nanoparticles that were swollen in THF. The d_(n) of thenanoparticles in water (a non-swelling solvent) was 12.0, and the d_(z)was 16.1.

Examples 20 and 21

The nanoparticle latexes of Examples 18 and 19 were then blended in aBrabender mixer with a standard solution styrene-butadiene rubber (std.S-SBR), having a 12% vinyl polybutadiene content, a 23.5% styrenecontent, a Mooney ML₄ at 100° C. of 55, and a T_(g) of −62° C. Furtherdetails of the blending are presented in Table 4.

TABLE 4 Example 20 Example 21 Std. S-SBR (phr) 100 100 Nanoparticlelatex used Ex. 18 Ex. 19 % nanoparticles in latex 26.34 23.24 g latexused 39.86 45.18 g nanoparticles used 10.5 10.5 phr, nanoparticles inmixture 30.00 30.00 % solids (inorganic salts) 3.15 3.31 v_(f) 0.20230.2023 Particle functionality Yes No Step Temp rpm Mins. Step Temp RpmMins. Mixing Rubber 105 50 1 Rubber 105 50 1 Conditions ⅓ 105 30 3 ⅓ 10530 3 (small Brabender latex latex mixer with a 59.5 ⅓ 105 30 3 ⅓ 105 303 cm³ working latex latex volume) ⅓ 105 30 3 ⅓ 105 30 3 latex latex 13030 3 130 30 3 140 50 2 140 50 2 Drop 25 Drop 25 Mix Number- 1 2 Average1 2 Average latex, charge, g 41.52 41.6 41.56 44.62 44.23 44.43 Latexused, g 40.86 40.93 40.90 43.49 43.48 43.49 Particles used, g 10.7610.78 10.77 10.11 10.10 10.11 phr, particles used 30.75 30.80 30.7828.88 28.87 28.87 v_(f) of particles in mix 0.2063 0.2066 0.2065 0.19620.1962 0.1962 Salts present, g 1.29 1.29 1.29 1.44 1.44 1.44 TYrecovery, g 47.05 47.07 47.06 46.55 46.54 46.55 Actual recovery, g 46.5346.1 46.32 43.7 46.16 44.93 % recovered 98.9% 97.9% 98.4% 93.9% 99.2%96.5%

Examples 22-25

In Examples 22 and 23, the nanoparticle/solution SBR blends of Examples20 and 21 were blended with dried rubber in a small Brabender mixer byfirst adding solution polymerized SBR having a 12% vinyl polybutadienecontent, a 23.5% styrene content, a Mooney ML₄ at 100° C. of 55, and aT_(g) of −62° C. Then the nanoparticle latex was added as shown in Table4. The nanoparticles were employed as the only filler in the rubber andwere calculated to have a filler volume fraction (v_(f)) ofapproximately 0.2.

In Examples 24 and 25, a control with 50 phr CB was prepared with thisrubber and had the same v_(f) as the nanoparticles. Example 25 differsfrom Example 24 in that 4 phr of the SBR was replaced with 4 phr ofsodium dodecyl sulfate. Additional sodium dodecyl sulfate surfactant wasadded in Example 25 to demonstrate whether the surfactant had any effecton the properties. It did not show any relevant effect. The densitydifference between the two fillers thus allows a lower density filledrubber stock to be prepared. The nanoparticles of Examples 22 and 23have an approximate density of 1.1 g/cc as compared to the carbon blackof Example 24 at approximately 1.8 g/cc.

Table 5 and FIGS. 2-5 report further details of Examples 22-25.According to these teachings, significant reductions in compound densityand 60° C. tan δ (e.g. 5% or more) may be possible.

TABLE 5 Ex. 22 Ex. 23 Ex. 24 Ex. 25 Std. S-SBR (phr): 100 100 100 96 CB(N339) (phr): 50 50 Example 18 nanoparticles (IPO 30 functionalized)Example 19 nanoparticles 30 Sodium Dodecyl Sulfate (phr): 4 Stearic Acid(phr) 2 2 2 2 Zinc Oxide (phr) 2.5 2.5 2.5 2.5 Antioxidant (phr) 1 1 1 1Sulfur (phr) 1.3 1.3 1.3 1.3 DPG Accelerator (phr) 0.2 0.2 0.2 0.2 CBSAccelerator (phr) 1.7 1.7 1.7 1.7 Approx. Filler Volume fraction, v_(f):0.2 0.2 0.2 0.2 t50% [171° C. Cure] (min): 4.9 4.4 2.5 2.3 t90% [171° C.Cure] (min): 6.5 5.8 3.4 3.3 MH-ML [171° C. Cure] (dN-m): 11.8 10.6 18.917.8 ts5 [ML Scorch at 130° C.] (min): 52.8 39.1 17.6 16.6 ML1 + 4 @130° C.: 50.8 41.9 75.9 75.9 50% Modulus @ 23° C. (MPa): 0.97 0.85 1.571.62 300% Modulus @ 23° C. (MPa): 2.9 2.5 14.4 13.7 T_(b), Break Stress@ 23° C. (MPa): 5.7 5.6 15.7 16.9 E_(b), Elong. at Break @ 23° C. (%):537 533 322 357 tan δ [TS; 0° C.; 10 Hz, 2%]: 0.104 0.11 0.221 0.225G′(MPa) [TS; 0° C.; 10 Hz, 2%]: 5.72 4.79 10.67 13.46 tan δ [TS; 30° C.;10 Hz, 2%]: 0.1 0.106 0.196 0.208 G′(MPa) [TS; 30° C.; 10 Hz, 2%]: 4.673.82 7.46 9.23 tan δ [TS; 60° C.; 10 Hz, 2%]: 0.092 0.092 0.172 0.187G′(MPa) [TS; 60° C.; 10 Hz, 2%]: 4.02 3.37 5.95 6.93 Lambourn Wear Indexat 25% slip: 98 97 100 102 Cured Compound Density (g/cc): 1.005 1.0081.169 1.155 Decrease in Compound Density 14.0 13.8 0.0 1.2 (%):

Example 26

Preparation of Low Solids Latex of Styrene/Divinylbenzene Particles

To a 2 L resin kettle containing an N₂ inlet tube and an electricstirrer with a paddle blade was added 840.72 grams of oxygen-freedistilled water. Then 1.57 grams of sodium bicarbonate and 26.15 gramsof sodium dodecyl sulfate while added while maintaining the nitrogenpurge, while stirring at about 150 rpm and heating to 40° C. To thisaqueous solution was added 195.14 grams of 19.35% DVB/S monomer mixturethat had been extracted free of antioxidant. Immediately after themonomers were added, stirring was increased and 32 mL of a 0.037 Maqueous solution of potassium persulfate (prepared with oxygen freewater) was added. A white emulsion was initially formed that becameopaque within 10 minutes. The stirring was continued at 360 rpm and thetemperature was increased to 73° C. during the next 1.3 hrs. Thetemperature was held above 53° C. for the next 3 hours before 0.72 mL ofa 3.30M aqueous solution of 40% sodium salt of dimethyl dithiocarbamicacid was added to deactivate the remaining persulfate catalyst.

The emulsion was then removed from the reactor and allowed to cool. Uponcooling no odor of DVB, S or ES could be detected. The absence of DVB,S, or ES was confirmed by GC analysis.

A total of 1115.03 g of latex was obtained with a pH of about 7 asmeasured by a paper strip. The latex had a calculated nanoparticleconcentration of 17.28% and total solid concentration of 19.75%. Thenanoparticles that had a composition of 19.35% DVB were diluted with THFto provide swollen particles having average diameter as measured by FFFof: d_(n)=18.7 nm, d_(w)=21.5 nm and d_(z)=24.5 nm with a dispersion of1.15. Repeating the FFF using water as the media gave a d_(z) of 20.3nm.

Example 27

Example 24 was concentrated in a 1 L flask with a Roto-Vac, usingmoderate vacuum while heating the water bath to 36° C. to 42° C. over an8 hour period. The final concentrated latex obtained weighed 471.61 gand had a calculated concentration of 36.5% nanoparticles and 41.7%total solids.

Examples 28-30

For the mixing of nanoparticle latexes with dry solvent-free solutionpolymerized SBR (S-SBR) having a 12% vinyl polybutadiene content, a23.5% styrene content, a Mooney ML₄ at 100° C. of 55, and a T_(g) of−62° C., a ZSK-30 co-rotating twin screw extruder was used with theconfiguration listed on Table 6 below.

TABLE 6 Status for manual feeding at 20 rpm Zone Temp Port additionstatus Number ° C. Rubber and Latex 1 51 feed 2 116 closed 3 122 openfor venting 4 127 closed 5 126 extrusion

The aqueous nanoparticle latexes of Examples 19 and 27 were mixed withthe S-SBR by the sequence described above to give the products listed onTable 7. Each length of extrudate was mixed on a two roll mill with 10passes to ensure that the sample for subsequent analysis was homogenous.To conserve on materials three different mixes were sequentiallyprepared such that the amount of water that needed to be vented offduring the process could be evaluated. The results of this indicatedthat under the conditions chosen, the foam generated by the waterremoval was found to be mild enough to run continuously for the mixtureschosen.

TABLE 7 Latex Rate Latex Nanoparticle S-SBR Latex mL/30 CollectedObserved Charge Example conc. wt. % gm. mL sec gm. Venting wt. % Example28 27 36.5 58 45 2.0 64 Trace 0.221 Example 29 27 36.5 58 90 4.0 94Slight foam 0.362 Example 30 19 23.2 58 73 3.1 65 Moderate foam 0.226

A solid state NMR technique was developed to determine the trueconcentration of the nanoparticles in the rubber.

Examples 28A-30A

In Examples 28A-30A the volume fraction of the components in Examples28-30 were determined by NMR analysis. ¹³C MAS NMR studies wereconducted on a Varian Inova spectrometer interfaced to a Doty 5 mmdouble resonance NMR probe operating at an external magnetic fieldstrength of 11.7 T (corresponding to an observational frequency of125.68 MHz for ¹³C). An rf-field strength of 45 kHz was used and thespinning speed regulated to 3500 Hz. A total of 15,000 transients wereacquired while simultaneously decoupling 1H. For the spectrum in FIG. 5Ca 4 mm Doty probe operating at a spinning speed of 10 kHz was used.

FIG. 5 shows: A.) a ¹³C liquid state NMR spectrum of ethyl styrene,styrene, and divinyl benzene monomers; and ¹³C MAS NMR solid statespectra plotted with normalized intensity of B.) sodium lauryl sulfate(a surfactant used in making nanoparticles), C.) dried nanoparticles ofExample 1 containing sodium lauryl sulfate, and D.) the Example 21nanoparticle and SBR rubber blend (which included the nanoparticles ofExample 1.

Attempts to perform ₁₃C liquid state NMR of the aqueous nanoparticlelatex was unsuccessful and only resonances from the SLS were observed.This observation is attributed to the size, rigidity, and highlycrosslinked structure of the nanoparticles in the latex preventing theparticles from rapidly reorienting themselves thus causing resonances tobe significantly broadened and, therefore, unobservable on the timescaleof the experiment. To confirm, an aliquot of the aqueous nanoparticlelatex was placed in a beaker and allowed to air dry for 72 hours afterwhich time the dried nanoparticle composition was analyzed by ¹³C MASNMR (FIG. 5C). Results confirm that the line shapes for thenanoparticles are significantly broad compared to the SLS (FIG. 5B).

The ¹³C MAS NMR spectrum of the SBR polymer with nanoparticles (FIG. 5D)indicated almost an identical spectrum to what is expected from a pureSBR. The only clearly resolved peaks between the SBR polymer, the DVB,ES and S of the nanoparticles, and the SLS are the methyl peak on theES, observable as a broad resonance near 15 ppm (FIG. 5C), the methylpeak of the SLS, observable as a broad peak at 14.3 ppm (FIG. 5B), andthe vinyl peaks of the SBR polymer and ethyl styrene DVB monomermixture, observable at 142 ppm and 115 ppm (FIGS. 5A and 5D). This setof spectra also demonstrate there is substantially no unsaturation inthe core of the nanoparticles attributed to the vinyl peaks shown in theFIG. 5A monomer mixture, as such peaks are not present or at least areso small as to be lost in the noise in the spectrum of the formednanoparticles in FIG. 5C. A peak resulting from unreacted vinyl monomermay be present at about 112 ppm, but it is too small to be identifiedover the noise.

The vinyl peaks can be used to determine the amount of SBR since the ES,S, and DVB in the nanoparticles should be fully polymerized in thescheme used. The relative amount of ES and S, to DVB was readilymeasured from the starting material and when mixed with S it was foundto be 1.0 to 1.3 to 5.4 moles of ES to DVB to S monomer. Also known isthe weight percent of vinyl, styrene, and 1,4 BD in the Std. S-SBRstarting material (11% vinyl (polybutadiene), 22.5% styrene). Despitethe significant spectral overlap between the nanoparticles and the SBRpolymer, therefore, the amount of nanoparticles in the sample can bequantified (Table 8) by using the areas of the vinyl resonances, whichonly arise from the SBR, the methyl peak of the ES, which is only fromthe nanoparticles, and the methyl peak for the sodium lauryl sulfate(SLS) at 14.5 ppm through the equations

${{Vinyl}\mspace{14mu} (g)} = {\frac{{Area}_{{Vinyl}\mspace{14mu} {({142\mspace{14mu} {ppm}})}} + {Area}_{{Vinyl}\mspace{14mu} {({115\mspace{14mu} {ppm}})}}}{2}54\mspace{14mu} {g/{mol}}}$Ethyl  Styrene  (g) = (Area_(Methyl(15.5ppm)))130  g/molSLS(g) = (Area_(SLS − Methyl(14.5ppm)))288  g/mol

Through the appropriate mass balance the amount of S and 1,4 BD can becalculated from the mass of vinyl. Likewise, the amount of polystyreneand DVB in the nanoparticles can be calculated from the mass of ESallowing the total weight percent of each component in the mixture to bedetermined as reported in Table 8 (all values reported by weight).

TABLE 8 1,4 Ethyl Vinyl Styrene BD Styrene DVB Polystyrene NanoparticlesSLS Example 28 7.1 17.4 54.5 3.0 3.8 12.6 19.4 1.7 Example 29 6.3 15.348.0 4.1 5.2 17.3 26.6 3.8 Example 30 6.8 16.6 52.1 3.4 4.3 14.3 22.02.6

Examples 31-36

In examples 31-36 the nanoparticle/elastomer blend of Examples 28-30were compounded in a Brabender mixer and cured. Examples 35 and 36 werecontrol examples filled with carbon black. The polymer and fillercomponent of Examples 31 and 32 were comprised entirely of the extrusionblend from Examples 28 and 29 to give 0.10 and 0.25 nanoparticle ofstocks in the mixer. Example 33 was blended with the S-SBR to produce acomposition with 24.15 phr of nanoparticle filler. In Example 34, unusedportions of Examples 31 and 32 were blended to give a desired 31.71 phrfiller. Examples 33 and 34 were prepared to have matching of 0.167 and0.205 with the Control Examples 35 and 36 that were filled with N339carbon black.

Examples 31-36 were further compounded with 2.5 phr ZnO, 2.0 phr stearicacid, 1.0 phr antioxidant in a 160° C. Brabender having an internalvolume of 59 cc with a cam rotor. The final mix was also done in thesame Brabender with 1.3 phr sulfur and 1.9 phr accelerators at 90 to110° C. Curing at 171° C. produced the composition on which the propertyvalues reported in Table 9 were determined.

The polymer and nanoparticle dry blends from the extruder were dilutedwith the S-SBR to achieve a desired volume fraction by conventionalrubber mixing techniques. The carbon black-filled Examples 35 and 36were mixed in the same manner. The volume fraction reported below wasdetermined by NMR and checked by pyrolysis.

Table 9 reports further details of the compositions and theirproperties.

TABLE 9 Ex. 31 Ex. 32 Ex. 33 Ex. 34 Ex. 35 Ex. 36 Polymer/NP Dry Blendfrom Extruder Ex. 28 Ex. 29 Ex. 30 blend none none NP identity Ex. 27Ex. 27 Ex. 19 blend none none Filler, nanoparticle d_(n) or (CB type)18.7 18.7 18.7 18.7 N339 N339 Filler, v_(f) 0.100 0.248 0.167 0.2050.167 0.205 Filler, phr 13.24 40.00 24.15 31.71 39.53 51.00 50% Modulus@ 23° C. (MPa) 0.82 1.08 0.79 1.02 1.19 1.57 300% Modulus @ 23° C. (MPa)2.84 3.21 2.38 3.08 11.02 14.91 Tensile Break Stress @ 23° C. (MPa) 2.816.84 3.64 5.19 14.26 17.38 Elongation at Break @ 23° C. (%) 294 535 430463 359 340 Toughness @ 23° C. 4.45 16.74 8.01 11.91 21.26 25.55 100%Modulus @ 100° C. (MPa) 1.04 1.03 0.97 1.06 1.9 2.55 Tensile BreakStress @ 100° C. (MPa) 1.43 2.22 1.47 1.96 6.71 8.70 Tensile BreakStress @ 100° C. (MPa) 1.43 2.22 1.47 1.96 6.71 8.70 Elongation at Break@ 100° C. (%) 170 309 210 265 237 226 Toughness @100° C. 1.43 3.97 1.883.09 6.45 8.14 tan δ [SS; 60° C.; 10 Hz, 5%] 0.1136 0.1952 0.1339 0.17470.1716 0.1976 G′(MPa) [SS; 0° C.; 10 Hz, 5%] 2.658 9.09 3.099 6.2884.771 6.77 G′(MPa) [SS; 30° C.; 10 Hz, 5%] 2.189 6.818 2.551 4.566 3.4895.069 G′(MPa) [SS; 60° C.; 10 Hz, 5%] 1.873 4.99 2.027 3.319 2.841 3.913ΔG′(MPa) [SS; 0° C.; 10 Hz, 0.25%-14.25%] 1.025 9.031 1.289 4.836 4.3048.611 ΔG′(MPa) [SS; 30° C.;] 0.885 7.36 1.228 3.851 2.824 6.116 ΔG′(MPa)[SS; 60° C.; 10 Hz, 0.25%-14.25%] 0.692 5.25 0.837 2.427 1.938 3.729 25%Lambourn Index 1.50 0.91 1.21 1.01 1.00 0.81

The strain sweep (SS) of Examples 31-37 is shown in FIG. 6 and showsthat nanoparticles at low strains have lower values in tan δ than thecarbon black filled elastomers. However, the nanoparticles do not show adecrease in the tan δ at the highest strain levels. Overall, thenanoparticles show unexpected rubber reinforcement.

1. A polymeric composition comprising: nanoparticles having a polymeric core comprising vinyl-aromatic mono-vinyl monomer contributed units crosslinked with a multifunctional crosslinking agent that is polymerizable through an addition reaction; the polymeric core being essentially free of units of unsaturation; the polymeric core having a weight average particle diameter of about 10 nanometers to about 500 nanometers as determined by field flow fractionation on a sample swollen in THF solvent; and a latex elastomer having a number average molecular weight of at least about 150 kg/mol.
 2. The polymeric composition of claim 1, wherein the nanoparticles are present in a volume fraction of the polymeric composition of about 0.3 to about 0.5.
 3. The polymeric composition of claim 1, wherein the nanoparticles further comprise heterocyclic monomer contributed units.
 4. The polymeric composition of claim 1, wherein the nanoparticles are present in a volume fraction of the composition of about 0.4 to about 0.5.
 5. The polymeric composition of claim 1, wherein the nanoparticles have a weight average diameter of about 10 to about 500 nm as determined by field flow fractionation in THF.
 6. The polymeric composition of claim 1, wherein the nanoparticles include about 0.1 to about 30 weight percent of a heterocyclic monomer contributed unit.
 7. The polymeric composition of claim 6, wherein the multifunctional crosslinking agent is included in a weight equal to about 0.1 to about 20 weight percent of the heterocyclic monomer contributed unit.
 8. The polymeric composition of claim 1, wherein the nanoparticles have a density of about 0.8 to about 1.5 g/cc.
 9. The polymeric composition of claim 1, wherein the latex elastomer comprises a carboxyl functional group.
 10. The polymeric composition of claim 1, wherein the latex elastomer comprises a carboxylated poly(styrene-butadiene).
 11. A composition comprising: an elastomer; polymeric nanoparticles, wherein the polymeric nanoparticles include a copolymer comprising vinyl-aromatic monomer contributed units and heterocyclic monomer contributed units, the copolymer being crosslinked with a multifunctional crosslinking agent that is polymerizable through an addition reaction; wherein the composition is sulfur vulcanized, and the polymeric nanoparticles are present in a volume fraction of the composition of about 0.3 to about 0.5.
 12. The composition of claim 11, wherein the polymeric core is essentially free of units of unsaturation.
 13. The composition of claim 11, wherein the elastomer includes a functional group selected from the group consisting of: hydroxyl, carboxyl, and hydroxylaromatic.
 14. The composition of claim 11, wherein the elastomer comprises a carboxyl functional group.
 15. The composition of claim 11, wherein the elastomer comprises a carboxylated poly(styrene-butadiene).
 16. The composition of claim 11, wherein the vinyl-aromatic monomer is selected from the group consisting of: styrene, alpha-methylstyrene, 1-vinyl naphthalene, 2-vinyl naphthalene, 1-alpha-methyl vinyl naphthalene, 2-alpha-methyl vinyl naphthalene, vinyl toluene, isomers of vinyl toluene, 2-, 3-, and 4-substituted vinyl toluene, and 2-, 3-, or 4-ethyl styrene, methoxystyrene, t-butoxystyrene, and alkyl, cycloalkyl, aryl, alkaryl, and aralkyl substituted aromatic groups in which the total number of carbon atoms is not greater than
 18. 17. The composition of claim 11, wherein the composition is vulcanized.
 18. The composition of claim 11, wherein the nanoparticles are present in a volume fraction of the composition of about 0.4 to about 0.5.
 19. The composition of claim 11, wherein the nanoparticles are present in a volume fraction of about 150° C. to about 200° C.
 20. The composition of claim 11, further comprising carbon black, silica, or both. 